Gate structure of semiconductor device and method of forming same

Abstract

A semiconductor device and a method of forming the same are provided. A method includes forming a fin extending from a substrate. A sacrificial gate electrode layer is formed along a sidewall and a top surface of the fin. A patterning process is performed on the sacrificial gate electrode layer to form a sacrificial gate electrode. A reshaping process is performed on the sacrificial gate electrode to form a reshaped sacrificial gate electrode. The reshaped sacrificial gate electrode includes a first portion along the top surface of the fin and a second portion along the sidewall of the fin. A width of the first portion decreases as the first portion extends from a top surface of the first portion toward the top surface of the fin. A width of the second portion decreases as the second portion extends from the top surface of the fin toward the substrate.

What is claimed is: 
     
       1. A method comprising:
 forming a fin extending from a substrate; 
 forming a sacrificial gate electrode layer along a sidewall and a top surface of the fin; 
 performing a patterning process on the sacrificial gate electrode layer to form a sacrificial gate electrode, wherein the patterning process exposes the top surface of the fin, and wherein the patterning process forms a footing portion extending along the sidewall of the fin and a sidewall of the sacrificial gate electrode; and 
 performing a reshaping process on the sacrificial gate electrode to form a reshaped sacrificial gate electrode, wherein the reshaping process removes the footing portion, and wherein the reshaped sacrificial gate electrode comprises:
 a first portion along the top surface of the fin, wherein a width of the first portion decreases as the first portion extends from a top surface of the first portion toward the top surface of the fin; and 
 a second portion along the sidewall of the fin, wherein a width of the second portion decreases as the second portion extends from the top surface of the fin toward the substrate. 
 
 
     
     
       2. The method of  claim 1 , wherein performing the patterning process on the sacrificial gate electrode layer comprises performing a first etch process on the sacrificial gate electrode layer, wherein performing the reshaping process on the sacrificial gate electrode comprises performing a second etch process on the sacrificial gate electrode, and wherein the second etch process is different from the first etch process. 
     
     
       3. The method of  claim 2 , wherein the second etch process comprises a plasma etch process. 
     
     
       4. The method of  claim 1 , wherein the first portion of the reshaped sacrificial gate electrode has a sloped sidewall. 
     
     
       5. The method of  claim 1 , wherein the second portion of the reshaped sacrificial gate electrode has a sloped sidewall. 
     
     
       6. The method of  claim 1 , wherein the second portion of the reshaped sacrificial gate electrode has a curved sidewall. 
     
     
       7. The method of  claim 6 , wherein the curved sidewall is a concave sidewall. 
     
     
       8. The method of  claim 1 , further comprising:
 removing the reshaped sacrificial gate electrode to form an opening; and 
 forming a replacement gate stack in the opening. 
 
     
     
       9. A method comprising:
 forming a fin extending from a substrate; 
 forming an isolation region over the substrate and adjacent the fin, wherein the fin extends above a top surface of the isolation region; 
 depositing a sacrificial gate electrode layer along a sidewall and a top surface of the fin and along a top surface of the isolation region; 
 performing a first etch process on the sacrificial gate electrode layer to form a sacrificial gate electrode, wherein the first etch processes exposes the top surface of the isolation region, and wherein the first etch process forms a footing portion in physical contact with the top surface of the isolation region and a sidewall of the sacrificial gate electrode; and 
 performing a second etch process on the sacrificial gate electrode to form a reshaped sacrificial gate electrode, wherein the second etch process removes the footing portion, wherein the second etch process is different from the first etch process, and wherein the reshaped sacrificial gate electrode comprises:
 a first portion along the top surface of the fin, wherein a first width of the first portion at a top surface of the first portion is greater than a second width of the first portion at the top surface of the fin; and 
 a second portion along the sidewall of the fin, wherein a third width of the second portion at the top surface of the fin is greater than a fourth width of the second portion at the top surface of the isolation region. 
 
 
     
     
       10. The method of  claim 9 , wherein the second etch process is a plasma etch process. 
     
     
       11. The method of  claim 9 , wherein the second width is greater than the third width. 
     
     
       12. The method of  claim 9 , wherein the second width is equal to the third width. 
     
     
       13. The method of  claim 9 , further comprising:
 etching the reshaped sacrificial gate electrode to form an opening; and 
 depositing a conductive material in the opening to form a replacement gate stack. 
 
     
     
       14. The method of  claim 9 , wherein the first portion of the reshaped sacrificial gate electrode has a first sloped sidewall, and wherein the second portion of the reshaped sacrificial gate electrode has a second sloped sidewall. 
     
     
       15. The method of  claim 9 , wherein the first portion of the reshaped sacrificial gate electrode has a sloped sidewall, and wherein the second portion of the reshaped sacrificial gate electrode has a curved sidewall. 
     
     
       16. A method comprising:
 forming a fin extending from a substrate; 
 forming a sacrificial gate electrode layer along a sidewall and a top surface of the fin; 
 performing a first etch process on the sacrificial gate electrode layer to form a sacrificial gate electrode, wherein the first etch process comprises a dry etch process performed with an etchant mixture comprising a Br-containing gas, a Cl-containing gas, a N-containing gas, a F-containing gas, an O-containing gas, or a combination thereof; and 
 performing a second etch process on the sacrificial gate electrode to form a reshaped sacrificial gate electrode, wherein the second etch process comprises a plasma etch process performed using a plasma generated from a gas mixture comprising chlorine gas (Cl 2 ), and wherein the reshaped sacrificial gate electrode comprises:
 a first portion along the top surface of the fin, wherein a width of the first portion decreases as the first portion extends from a top surface of the first portion toward the top surface of the fin; and 
 a second portion along the sidewall of the fin, wherein a width of the second portion decreases as the second portion extends from the top surface of the fin toward the substrate. 
 
 
     
     
       17. The method of  claim 16 , wherein the gas mixture further comprises O 2 , H 2 , Ar, F 2 , Br 2 , N 2 , Xe, Kr, or a combination thereof. 
     
     
       18. The method of  claim 16 , wherein the dry etch process is performed for a time between about 400 sec to about 1200 sec. 
     
     
       19. The method of  claim 16 , wherein the plasma etch process is performed at a temperature between about 30° C. and about 150° C. 
     
     
       20. The method of  claim 19 , wherein the plasma etch process is performed for a time between about 20 sec and about 100 sec.